Large optical telescopes are used to view astronomical objects such as stars and galaxies and to collect data for measurement and scientific analysis. A schematic representation of a telescope 100 is shown in FIG. 1 where light from astronomical objects such as stars 102 is reflected in a mirror 104, and the reflected light 106 is focused on the telescope's focal plane where a field plate 108 is positioned. This reflected light 106 is captured by optical fibres 110 and fed to one or more spectrographs 112 for data measurement and analysis. Typically hundreds of fibres are used. The collecting end points 114 of the respective fibres are positioned at the field plate 108 with sufficient precision so that reflected light from specific astronomical objects can be collected. Therefore, for each different field of stars and galaxies all the fibres need to be repositioned appropriately.
One type of fibre positioning technology used to position the fibres on the field plate is shown in FIG. 2A. Multiple cassettes 202 are situated around a metal field plate 204 of the telescope and each cassette 202 houses a number of optical fibres (typically 10). The cassettes 202 use spring loaded retractors to keep the fibres straight when they are placed on the field plate 204. Each fibre has a fibre end point 206 and these end points 206 are positioned on the field plate 204 by a pick and place machine 208, such as a 2 Degree Field (2 dF) robotic fibre positioner. The 2 dF positioner picks up one end point 206 at a time and places it in the correct position and the fibre end points are then anchored to the metallic field plate 204 magnetically. This positioning process is complex, time consuming and reduces the amount of observing time available to the astronomer because of how long it takes to position the fibre end points.
Referring to FIG. 2B, each fibre end point 206 is connected to a magnet 210 that is used to anchor the end point to the metallic field plate 204. In order for each fibre 212 to capture the light reflected from the telescope's mirror (indicated by arrow 214) each fibre end point 206 also requires a prism 216 that bends the reflected light into the fibre. The construction of such a fibre end point is therefore quite bulky, requiring both a magnet and a prism.
Large telescopes that have several large multi-object spectrographs result in large slit-lengths so that very large numbers of fibres are required to fill the slits. Because of the use of cassettes as well as the time the positioning takes the number of fibres that can be accommodated is limited. Other problems include the spring loaded configuration resulting in unwanted forces exerted on the positioner and fibres crossing the focal plane when the end points are positioned. As the number of fibres increases, these problems also increase.
Because of the many disadvantages associated with existing positioning methods it is desirable to have an alternative way of positioning and anchoring optical fibres in large telescopes.
Reference to any prior art in the specification is not, and should not be taken as, an acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in Australia or any other jurisdiction or that this prior art could reasonably be expected to be ascertained, understood and regarded as relevant by a person skilled in the art.